The invention relates to an apparatus for mass transfer between a hot gas stream and a liquid in which the liquid is sprayed into the hot gas stream. The apparatus consists in principle of a gas feed pipe, which discharges vertically into an injection chamber arranged coaxially with it, which is wider than the gas feed pipe and converges conically in the flow direction, the upper part of the injection chamber being formed by an annular roof joined to the gas feed pipe and having liquid nozzles inserted in it, and a heat- and mass- transfer duct connected coaxially to the injection chamber.
A similarly constructed apparatus, which enables industrial waste gases to be treated with a wash liquid, is known from DE-A 2 303 131. With such apparatuses it is also frequently sought to achieve, in addition to the adsorption of harmful substances and the retention of dust particles, the cooling of the gas stream.
In the treatment of hot gases, the transition zone from parts of the wall which are exposed to the dry hot gas to parts of the wall which are wetted or sprayed with liquid proves to be very exposed to corrosion. This critical disadvantage occurs to a particularly high degree if the wetting boundary, as a result of instabilities in the liquid jets or the gas flow or also through load changes in the flow of gas to be treated, shifts to and fro. Serious corrosion effects are also observed if cold liquid drops climb up the gas feed pipe and impinge on the tube's hot internal wall. At these points, owing to the thermal shock, a severe erosion of material occurs, which is also followed by corrosion phenomena.
Consequently the use of cheaper materials, such as rubberized steel, is excluded. Under the alternating thermal stress, even high-grade materials such as alloys of nickel, chromium and molybdenum, achieve fairly long on-stream times only when the corrosive constituents in the gas and in the liquid are of a relatively harmless nature.
As a result of the erosion and corrosion effects described, the on-stream time and consequently the availability of the mass-transfer apparatus is impaired. The invention is based on the problem of minimizing such corrosion phenomena by constructional measures relating to direction of the flow and by this means improving the on-stream times.